.box1 {
  width: 100px;
  height: 200px;
}
.box2 {
  width: 200px;
  height: 200px;
}
/* 参数的默认值 */
.box1 {
  width: 100px;
  height: 200px;
  color: blue;
}
.box2 {
  width: 200px;
  height: 200px;
  color: blue;
}
